1. Field of the Invention
The present invention relates to a piezoelectric vibration device used, for example, as a band filter and, more particularly, to improvements in a piezoelectric vibration device including a plurality of resonance sections provided on a piezoelectric substrate and having a slit arranged to suppress interference between the resonance sections.
2. Description of the Related Art
Energy-trap type piezoelectric filters including a plurality of resonance sections provided on a piezoelectric substrate are known. In this type of piezoelectric filter, since a plurality of resonance sections are provided on the same piezoelectric substrate, a slit is provided in the piezoelectric substrate so as to suppress interference between the resonance section. For example, in Japanese Unexamined Utility Model Publication No. 58-135128, a piezoelectric vibration device is constructed such that two resonance sections are provided on a rectangular piezoelectric substrate, and a slit is provided between the resonance sections so as to extend from one side of the piezoelectric substrate toward the center.
Further, in Japanese Unexamined Utility Model Publication No. 1-59326, a piezoelectric vibration device includes a plurality of vibration sections provided on a piezoelectric substrate and a slit provided between the vibration sections in order to suppress interference between the vibration sections, and lead mounting electrodes are provided on both shoulder sections near the notched opening of the slit. By bonding one lead terminal so as to extend over the lead mounting electrodes on both shoulders, interference between the resonance sections is suppressed, and deformation of the piezoelectric substrate and a decrease in the mechanical strength caused by the formation of the slit are suppressed.
However, in the conventional piezoelectric vibration device in which interference between the resonance sections is suppressed as a result of the slit being provided in the piezoelectric substrate, there is still a problem that although the resonance characteristics are satisfactory, the piezoelectric substrate may sometimes break or crack during handling because the mechanical strength is not sufficient as a result of the slit being formed in the piezoelectric substrate.